Carbofuran is a systemic insecticide, acaricide, and nematicide currently manufactured and used in the United States and throughout the world. The product can be produced by the sequential conversion of o-nitrophenol to 2-beta-methallyloxynitrobenzene, 2,3-dihydro-2,2-dimethyl-7-nitrobenzo-furan, 2,3-dihydro-2,2-dimethyl-7-benzofuranol, and finally 2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl carbamate as described in U.S. Pat. No. 3,320,286 which issued to FMC Corporation on May 16, 1967. However, the major disadvantages of the process are the expense and difficulty encountered in the preparation.
The most current procedures for the preparation of carbofuran as disclosed in the patent literature involve the alkylation of a 2-substituted phenol or phenol per se with beta-methallyl chloride, followed by a Claisen rearrangement. The product, the 7-substituted-2,3-dihydro-2,2-dimethylbenzofuran, is then subjected to further transformations on the functional group at the 7-position in order to produce the desired benzofuranol. One process currently believed to be in use for the preparation of carbofuran is described in U.S. Pat. No. 3,320,286 and involves five distinct steps.
The process which involves the conversion of the aminobenzofuran to the benzofuranol via the diazonium salt is hazardous and requires special care in handling due to the potentially explosive nature of diazo salts. Thus, prior to the present invention, there was no simple process which utilized relatively inexpensive materials and avoided the hazards associated with diazonium salts.
Accordingly, one or more of the following objects can be achieved by the practice of this invention. It is an object of this invention to provide an improved process for the preparation of carbofuran and certain novel intermediate products. Another object of this invention is to provide a process which is simple and employs readily available and inexpensive starting materials. A further object is to provide a process which utilizes 1,2-cyclohexanedione as the starting material. Another object of the invention is to provide a simple two step process for the preparation of carbofuran phenol. These and other objects will readily become apparent to those skilled in the art in the light of the teachings hereinafter set forth.